Radiation source dependence of device performance degradation for 4H-SiC MESFETs

The impact of radiation source dependence on the device performance degradation of 4H-SiC MESFETs (Metal Schottky Field Effect Transistors), which have been irradiated at room temperature with 2 MeV electrons and 20 MeV protons, is studied. No performance degradation is observed by 1×1015 e/cm2 and 5×1011 p/cm2, while a slight increase of the linear drain current together with a decrease of the threshold voltage are noticed above higher fluence. The damage coefficient for protons is about three orders of magnitude larger than that for electrons. The radiation source dependence of the device performance degradation is attributed to the difference of mass and the possibility of nuclear collision for the formation of lattice defects. Based on thermal annealing results of electron-irradiated MESFETs, it is found that the recovery of the drain current characteristics principally takes place from 100 ∘C, and that the drain current recovers to the pre-rad value after 200 ∘C annealing. On the other hand, capacitance and induced deep levels do not recover by 200 ∘C annealing. It is concluded that the degradation of the drain current is mainly sensitive to the radiation-induced decrease of the Schottky barrier height at the gate contact.